Building adaptive applications: on the need for congestion control
Colin S. Perkins · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
While the convergence of video communication networks and the Internet has many benefits, a number of issues arise when adapting video conferencing and streaming media systems to run on IP networks. One of the major problems is the lack of deployed quality-of-service support, meaning video applications must compete for resources with other best-effort traffic. Since the other traffic is overwhelmingly TCP/IP-based, video applications must either use TCP/IP themselves or behave in a TCP-Friendly manner to ensure the stability of the network. This paper describes why using TCP/IP directly is often inappropriate, explores the problems inherent in adapting video codec output to match the behaviour of the network using a TCP-Friendly protocol, and discuss the trade-off between network friendly behaviour and video quality. Potential solutions such as TFRC and DCCP are discussed, and their standardization status noted. The aim of the work is to highlight problems and areas where further research is needed – both for network protocol designers, video codec developers, and application authors – with the aim of fostering better network aware codecs.